Method and apparatus for construction of aircraft and the like



H. KLEMM METHOD AND APPARATUS FOR CONSTRUCTION OF AIRCRAFT AND THE LIKEAug. 1, 1939.

Filed Nov 27, 1937 Fig.2

Hg ns Klemm Patented Aug. 1, 1939 UNITED STATES "PATENT; OFFICE IVIETHODAPPARATUS FOR CONSTRUC- TION F AIRCRAFT AND THE LIKE Hanns Klemm,Boblingen, Germany, assignor to William Rhodes Davis, New York, N. Y.

Application November 27, 1937, Serial No. 176,780 In Germany November 5,1936 3 Claims. (01. 244-120) least to some extent, to the strength. Inany" case the covering skin is stretched, on the frame work, or .thecovering plates, after having been previously bent as far as possible tothe correct shape, are laid upon the framework erected after the mannerof a ship built on the stocks, and secured thereto.

According to the invention, a method of construction is .used whichconsists primarily in sub- '1 dividing the shell body to be constructedinto longitudinal shell segments substantially free from intersection,and in producing said segments individually by inserting thelongitudinal and transverse stiffening and stabilizing members, whichenable the skin to take up higher compression loads into a mold,.stretching the skin portions over the whole arrangement and securing theskin to the stiffening members. In contradistinction to the mold ofconstruction used hitherto, in which the result depended to a largeextent on the skill of the workers, the new mode of construction permitsfactory production by substantially unskilled labor. Only the fitter whoprepares the mold and, at the most, ,places the stabilizing members inposition must be a skilled worker,- while everything else can be left toordinary unskilled labor. The whole process of inserting the stiffeningmembers is substantially an operation of inserting ready made parts intoa fixed 85 mold, nothing further needing to be measured off, so thatmistakes can hardly occur. The mounting of the skin, furthermore,consists in simply pressing the same onto the mold, which prevents theskin plates from being bent out of shape, and

then in gluing,'or otherwise securing it to the stabilizing members. Inaddition to economical and rapid manufacture, high accuracy anddependability of the product are obtained.

In the case of wooden constructions l'provide an advantageous featureaccording to whichwooden stiffening are embedded in the mold and outerskin parts of-plywood are stretched over the mold and glued. on tostiffenings previously coat-- ed with glue. In this process thecore-like mold,

5; inserted in h l e s 'the m ld a d lo gitudinal members are insertedinto cut-outs of the transverse members. Then, in consequence of theusually quite flatshape and parallel position of the transverse members,less extensive sub-division of the whole structural body into individualsections or shells is possible,- without any difficulty arising inremoving the shell segments from the mold. r

The assembly of the finished sections or shells is advantageouslycarried out-by joining together inner straps or flanges running alongthe .free

edges of the segments, thus providing dependable,

easily made seam not affecting the outside ap-, pearance. Whereparticularly reliable joints are required, the frames may alternatelyextend from both sides over the partial joint and thus strengthen theunion by overlapping, or they may be joined by a butt joint andstrapping.

The building apparatus required for carrying out the new processconsists essentially of an uncollapsible core with beddings for thestabilizing members, and with intermediate filling bodies extending tothe outer surface of the stiifening the filling bodies and thestabilizing members. The filling bodies adjacent the edges of the moldare cut away inwardly from the desired inner shape. of the shell segmentto permit removal from the mold in radial direction of a shell seg-'ment formed on said mold with a stabilizing member secured theretoalong or adjacent the edge of the segment. This mold which supports theskin over practically its entire surface, prevents damage to the skineven if the worker lieswith his whole body on the workpiece. Thegapsbetween the filling bodies and stabilizing members prevent gluingtogether of the skin and the filling bodies and also facilitate theremoval of the finished segment from the mold.

The filling bodies are advantageously secured slidably orinterchangeably to the core; this permits the use of one and the samecore for different types of shells, vertical-adjustment of the fillingbodies enabling the whole shape to be varied substantially.

For the fitting of the skin" use is preferably made of belts which arecapable of being fastened to one or'both edges of the mold by means of.quick-fastening devices or, if desired, tension fasteners-similar tospring bottle caps, and which are ,made resilient or are resilientlylined, for 7 example with felt. Owing to the rounded shapes customaryfor aircraft 'fuselages, spars of sup-' porting structures and similarbodies, these tension belts provide for a good pressure on all .members,a gap preferably being left between sides to allow a solid gluing,soldering or other union to beefiected.

Referring to the drawing left herewith, the figures represent, asexamples only, the rear portion of the fuselage of an aircraft:-

Fi 1 is a cross-section of the mold with the workpiece enclosed;

Fig. 2 is a view from above of the mold during the work;

Fig.3 is a partial cross-section of two fuselage sections or shellsshowing the joint. I

As shown in Fig. 1, a support 2, similar to a bench and standing on legs1, carries a core 3, usually constructed of boards and strengthenedwhere required by ribs 4. Filling pieces 5 of the same height as thestabilizing members to be used, are secured on the core by means ofbolts 6 and straps 1 of smaller height (Fig. 2) pushed into the fillingbodies, hold the transverse stabilizing members 8, 9 in position; thebroader transverse inembers 9 may serve as a connecting element for theindividual transverse sections of the skin, if desired. Longitudinalstabilizing members ID are inserted into grooves in the transversemembers 8, 9, and edge flanges l l are similarly secured along the freeedges of the mold. The filling bodies 5 adjacent these edges are cutaway inwardly from the desired inner shape of the segment to permitremoval from the mold in radial direction of a shell segment formed onsaid mold and having said edge flanges ll secured thereto.

In this stage of construction the surfaces of the transverse members 8,9 and of the longitudinal members III, II together with the major partof the surfaces of the filling bodies 5 define the shape of the outerskin. Then glue is ap-/ plied to the members 8, 9, II], II, in the caseof a wooden construction, and sections of plywood skin l2 are stretchedover the mold with the help of felt-lined belts l3, which are held atone end in an eye l4 and are tightened at the other end, by arapid-fastening device l5.

After the glue has set, the belts l3 aredetached and the partial shellcomplete with its longitudinal and transverse stabilizing members isremoved in substantially radial direction from the mold, and made smoothat the edges along the edge spars H. The assembly is carried out bygluing together the edge flanges H and by gluing straps IS on to theframes 8, 9. The straps 16 may be held together by wooden pins i1 duringthe gluing, with the aid of additional springclamps, if necessary. Onthe other hand, the wooden pins maybe replaced by screws, while in thecase of-metal constructions screws alone may be used to secure thestraps.

In the process described the whole fuselage may be built in two halfsegments of the shell corresponding from the front to the rear. Ifnecessary, each half segment may be sub-divided transversely. Strongwing spars extending from theleading edge of the wing along the line ofaerodynamic centres ofthe wing, which have a cross-section similar tothat of a fuselage may be constructed in exactly the same way, or awhole, wing may be constructed in this manner in the form of a shell,the shell segments either covering the suction face and pressure face ofthe .wing, respectively, or constituting shell portions which are freefrom intersection and are joined togetherin a sectional plane beingperpendicular to the chord line of the wing and running along the wing.

Exactly the same type of procedure may be used for metal constructions,the stabilizing members and the skin segments being welded or solderedtogether. c

The field of utility of the invention comprises also, apart fromaircraft fuselages and carrying.

surfaces, struts, supports, fixed planes, control surfaces, wheelfairings and many ,other light construction hollow bodies;

I claim:

1. A method of building segments of light loadcarrying shells foraircraft fuselages, wings and the like, which segments are to besubsequently secured together, said method comprising the steps ofinserting a plurality of thin transverse and longitudinal stabilizingmembers loosely into grooves of a mold having a shape correspondingsubstantially to that of a longitudinal segment of the shell, allowingfor an appreciable clearance between the walls of the grooves and thestabilizing members, stretching a skin of thin, stiff material tightlyover said mold and loose stabilizing members while supporting the lattersubstantially in a position in which the outer surfaces thereof definewith the major part of the mold surface the desired inner shape of theshell segment, adhering said skin permanently to the entire outersurface of said longitudinal and transverse stabilizing members withoutpuncturing the skin while allowing the stabilizing members to.find theirown bearings against the skin, and removing the rigidly stabilized shellsegment with the afiixed stabilizing members in a substantially radialdirection from the mold.

2. A method of building segments of light loadcarrying shells foraircraft fuselages, wings, and the like, which segments are to besubsequently secured together, and consist each of a plurality of thintransverse and longitudinal stabilizing members and a skin of thin,stiff material attached to the outer surface of said stabilizingmembers, said method comprising the steps of inserting the transverseand longitudinal stabilizing members loosely into grooves of a moldhaving a shape corresponding substantially to that of a longitudinalsegment of.the shell, allowing for an appreciable clearance between thewalls of the grooves and the stabilizing members, applying glue to atleast oneof the surfaces of said stabilizing members and skin to bebrought into contact, stretching the skin of thin stiff material tightlyover said mold and loose stabilizing mem bers, while supporting thelatter substantially in a position in which the outer surfaces thereofdefine with the major part of the mold surface -the desired inner shapeof the shell allowing the loose stabilizing members to find their ownbearings against the skin, holding the skin on said mold until apermanent gluing connection has been established between the skin andthestabilizing members, and removing the rigidly stabilized shell segmentwith the longitudinal and transverse stabilizing members glued theretoin substantially radial direction from themold.

3. An apparatus for building light load-carrying shells for aircraft andthe like, comprising a mold of a shape corresponding substantially tothat of a longitudinal segment of such shell, said mold having a core,and filling bodies mounted on said core, said filling bodies beingshaped and arranged to substantially define the desired inner shape ofthe shell segment and to provide a plurality of longitudinal and oftrans-,

verse grooves for the insertion of thin stabilizin members, subdividingthe shell into panels, said grooves having a width sufiicientlyexceeding that of the stabilizing members to be inserted therein toallow for self-adjustment of said members to a skin to be applied tosaid mold, thefllling bodies adjacent said mold edges being cut awayinwardly from the desired inner shape of the shell segment to permitremoval in substantially radial direction from said mold of a shellseg-. ment'with the stabilizing member permanently adhered theretowithout puncturing of the applied skin.

- HANS KLEMM.

